Mould equipment for pipeline section coating and methods for coating of pipeline sections with moulds

ABSTRACT

A mold for coating a pipeline section with molten coating material from an injection molding machine, wherein the mold comprises a shell of impervious material reinforced by an exoskeleton of non-distensible material. An assembly for supporting a mold comprising a plurality of mutually separable shell bodies for coating a pipeline section, wherein the assembly comprises motorized opening and closing of the shell bodies in a straight line. An assembly for supporting a bent pipeline section wherein the assembly comprises a base and a pair of arms extending from the base, wherein each arm comprises a respective clamping collar for clamping a bent pipe section between the arms. A vehicle for induction heating a bent pipeline section, wherein the vehicle comprises: a helical induction coil; and wheels arranged to guide movement of both ends of the induction coil through a tubular inside face of a bent pipeline section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority, under 35 U.S.C. §119(a)-(d), to UKPatent Application No. GB 1314340.9 filed Aug. 9, 2013, the contents ofwhich are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to improvements in mold equipment forpipeline section coating, improvements in methods for making moldequipment and improvements in methods for coating of pipeline sectionswith molds.

BACKGROUND OF THE INVENTION

Pipelines in the oil and gas industry are typically formed from multiplelengths of steel pipeline sections that are welded together end-to-endas they are being laid. To prevent corrosion of the pipeline sectionsand to reduce heat loss of fluids transported by pipelines, the pipelinesections are coated with one or more protective or insulative layers.The pipeline sections are usually coated at a factory remote from thelocation in which they are to be laid. This is often referred to asfactory-applied coating and it is generally more cost effective thancoating pipeline sections on site where they are laid. At the factory,the coating is applied to the outside of the pipeline sections whereupona short length is left uncoated at either end of the pipeline section.The uncoated ends are necessary to enable the pipeline sections to bewelded together to form the pipeline in the field.

Polypropylene coating has good protective and insulative properties andit is commonly used to coat pipelines transporting fluids at up to 140degrees centigrade. Polypropylene is widely used for factory-appliedcoating for pipeline sections used to form pipelines. The pipe coatingcan take several different forms depending on the particular applicationand will normally consist of more than one layer. A conventional pipecoating will typically comprise a first thin layer of a primer, such asan epoxy-based material, that is applied in either liquid or powderedform to the outer surface of the steel pipeline section. To ensure agood bond between the pipeline section and the primer, the pipelinesection is typically blast cleaned and etched with an appropriate anchorpattern. A second layer of polypropylene chemically modified to act asan adhesive will then usually be applied over the primer during thecuring time (i.e. time taken to harden or set) of the primer. Whilecuring of the primer is ongoing, and so as to allow the all the layersto bond, a third layer is applied. Typically, the third layer ispolypropylene and a common process for coating pipelines withpolypropylene is the Injection Molded Polypropylene (IMPP) technique. AnIMPP coating is typically applied while the steel pipeline section isheated by induction heating, for instance. All but the ends of thepipeline section is enclosed by a heavy duty steel mold that defines acavity around the uncoated pipeline section, which is subsequentlyfilled with molten polypropylene from an IMPP injection molding machinein the factory. Control of the heating, so the factory-applied coatingis sufficiently heated to allow fusion to occur when the moltenpolypropylene is introduced into the mold, requires skill. The mold mustbe of heavy duty construction, often incorporating hydraulic opening andclosing mechanisms in order to withstand high molding pressures. TheIMPP injection molding machine which dispenses polypropylene into themold is normally closely coupled to the mold. Once the polypropylene hascooled and solidified, the mold is removed to leave the factory-appliedcoating in place on the pipeline section.

Before the pipeline can be laid the welded ends, known as field joints,must be coated in the region of the joint to prevent corrosion of thepipeline. The coating in these regions is referred to as the field jointcoating. Two common processes for coating field joints of pipelinesformed from polypropylene coated pipeline sections are the IMPPtechnique and an Injection Molded Polyurethane (IMPU) technique. Patentpublication No. WO2009/027686 discloses a filed joint coating techniquewhich permits fusion to occur between the pipe and the field jointcoatings.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a moldfor coating a pipeline section with molten coating material from aninjection molding machine, wherein the mold comprises a shell ofimpervious material reinforced by an exoskeleton of non-distensiblematerial. Casting and/or machining a special shape of pipeline sectionmold from steel is costly and time consuming. Once a steel mold has beenmade it can be used for only one shape of pipeline coating. The presentinvention provides a pipeline section mold that may be lighter, quickerto make and less expensive than a comparable mold made from solid steel.Advantageously, the pipeline section mold of the present invention has aversatile design that is readily adaptable to different shapes ofcoating. Its components may be recycled for use in various differentshapes of pipeline section molds.

Preferably, the exoskeleton is made from a plurality of parts. Theexoskeleton may be made from a kit of parts. The parts may be standardparts that may be assembled in different ways to suit customerpreferences, with or without specially commissioned parts to suitparticular shape of coating.

Preferably, the parts of the exoskeleton are interlocked. Thisfacilitates assembly and may improve structural rigidity of theexoskeleton.

Preferably, parts of the exoskeleton are made of steel. Steel is areadily available of non-distensible material with the sufficientrigidity to reinforce a mold for coating a pipeline section. Preferably,the steel parts of the exoskeleton are welded together. Welding mayprovide additional rigidity.

Preferably, the exoskeleton comprises parts contoured to complement aninside face of the shell. The exoskeleton may support the shape of theinside face.

Preferably, the mold comprises connection means for connecting the moldto an injection molding machine.

Preferably, the shell is made from molded material. Molded material islighter, quicker to make and less expensive than casting and/ormachining steel. Molded material is versatile since it may be moldedaccording to different shapes and sizes. The molded material may be anyimpervious material suitable for contact with molten pipeline sectioncoating material from an injection molding machine, like, for example,carbon fiber composite materials or plastic fiber composite materials.Preferably, the molded material is glass-fiber reinforced plastic.Glass-fiber reinforced plastic is readily adaptable to different usesand it is relatively inexpensive. If the molded material is glass-fiberreinforced plastic then its preferred thickness is at least 8 mm.

Preferably, the exoskeleton is at least partially embedded in the shell.This may enhance reinforcement provided by the exoskeleton and increaseadhesion to the shell.

Preferably, the shell comprises a plurality of mutually separable shellbodies each having a part of the exoskeleton and wherein the shellbodies are mutually connectable in a sealed relationship with a pipelinesection located in a cavity between the shell bodies. This allows theshell bodies to open and close thereby facilitating location of apipeline section inside the mold. Preferably, the shell bodies areseparable at a common central plane in a straight line normal to thecentral plane. Straight line opening of the shell bodies occupies lessspace around an entry point to the mold because the shell bodies can bemoved from above and/or below the shell bodies. This avoids having anopening mechanism beside the mold which could impede a pipelinesection's access. Straight line closing of the shell bodies may providea more even distribution of pressure that that provided by, for example,pivoting closing of the shell bodies in the manner of a clam shell.

The mold may be for coating an irregular pipeline section or a bentpipeline section. The versatility of the mold of the present inventionmakes it readily adaptable to different shapes of coating for variousshapes of pipeline section at a reasonable cost and within a reasonabletime scale.

Preferably, the mold is for coating a pipeline section with a coating ofmolten polypropylene or a coating of molten polyurethane as these arecommon coating material with suitable pipeline protection and insulationproperties.

Preferably, the mold comprises a section for connection to a moltencoating material delivery pipe from an injection molding machine. Thismay permit injection of molten coating material directly from aninjection molding machine.

According to a second aspect of the present invention, there is provideda method of making a mold for coating a pipeline section with moltencoating material from an injection molding machine, wherein the methodcomprises the steps of: (a) forming a shell body of impervious materialwith an inside face having the shape of a pipeline section coating; and(b) cladding the shell body with an exoskeleton of non-distensiblematerial. The present invention provides a pipeline section mold thatmay be lighter than a comparable mold made from solid steel and that maybe made in less time and for less expense. Advantageously, the presentinvention provides a method of making a mold that is versatile andreadily adaptable to different shapes of coating.

Preferably, the forming step comprises the steps of: (c) laying a shellbody of deformable curable material over a pipeline section coatingtemplate; (d) curing the shell body; and (e) removing the template fromthe shell body. A shell body that is deformable and curable may bemolded. The result is lighter shell body that is quicker to make andless expensive than casting and/or machining from solid steel. Moldedmaterial is versatile since it may be adopt different shapes and sizes.The molded material may be any impervious material suitable for contactwith molten pipeline section coating material from an injection moldingmachine, like, for example, carbon fiber composite materials or plasticfiber composite materials.

Preferably, the method comprises a step of assembling the exoskeletonfrom a plurality of parts. The exoskeleton may be made from a kit ofparts. The parts may be standard parts that may be assembled indifferent ways to suit customer preferences.

Preferably, the assembling step comprises interlocking parts of theexoskeleton. Interlocking the parts facilitates assembly and may improvestructural rigidity of the exoskeleton.

Preferably, the assembling step is preceded by a step of laser cuttingparts of the exoskeleton from steel. Laser cutting provides an accurateand versatile manufacturing technique which is also suited to makingspecially commissioned parts for a particular shape of coating.

Preferably, the assembling step comprises welding steel parts of theexoskeleton. Welding may provide additional rigidity.

Preferably, the forming step comprises laying a shell body over apipeline section coating template. Use of a template to form the shapeof the shell body facilitates accuracy. Preferably, the shell body isglass-fiber reinforced plastic. Glass-fiber reinforced plastic isreadily adaptable to different uses and it is relatively inexpensive. Ifthe shell body is made of glass-fiber reinforced plastic, then itspreferred thickness is at least 8 mm.

Preferably, the cladding step comprises at least partially embedding theexoskeleton in the shell body. This may enhance reinforcement providedby the exoskeleton and increase adhesion to the shell body. Preferably,the cladding step comprises keying the exoskeleton into the shell body.This may further increase adhesion between the exoskeleton and the shellbody.

Preferably, the method steps comprise making a mold having a pluralityof mutually separable shell bodies, each shell body being clad byexoskeleton. This allows the shell bodies to open and close therebyfacilitating location of a pipeline section inside the mold.

Preferably, the method steps comprise making a mold with an inside facehaving the shape of a coating for an irregular pipeline section or abent pipeline section. The method of the present invention is versatileand readily adaptable for making molds having different shapes forcoating various shapes of pipeline section at a reasonable cost andwithin a reasonable time scale.

According to a third aspect of the present invention, there is providedan exoskeleton for use in the second aspect of the present invention.

According to a fourth aspect of the present invention, there is provideda kit of parts for an exoskeleton for use in the second aspect of thepresent invention.

According to a fifth aspect of the present invention, there is provideda pipeline section coating template for use in the second aspect of thepresent invention.

According to a sixth aspect of the present invention, there is provideda kit of parts for a pipeline section coating template for use in thesecond aspect of the present invention.

Preferably, the pipeline section coating template comprises a multitudeof inter-connectable parts of varying shapes and sizes. This may enablethe kit of parts for a pipeline section coating template to be used,and/or re-used, for various different shapes and sizes of pipelinesections and pipeline section coatings.

According to a seventh aspect of the present invention, there isprovided an assembly for supporting a mold comprising a plurality ofmutually separable shell bodies for coating a pipeline section withmolten coating material from an injection molding machine, wherein theassembly comprises motorized opening and closing of the shell bodies ina straight line. Straight line opening of the shell bodies occupies lessspace around an entry point to the mold because the shell bodies can bemoved from above and/or below the shell bodies. This avoids having anopening mechanism beside the mold which could impede a pipelinesection's access. Straight line closing of the shell bodies may providea more even distribution of pressure that that provided by, for example,pivoting closing of the shell bodies in the manner of a clam shell.

Preferably, the assembly comprises adjustable support for supportingmolds of different sizes. Preferably, the assembly comprises adjustablesupport for supporting molds for coating irregular pipeline sections orbent pipeline sections.

Preferably, the motorized opening and closing is guided by rails. Thismay provide reliable and accurate movement of the shell bodies.Preferably, the motorized opening and closing is operable with apipeline section in the mold.

Preferably, the motorized opening and closing is operable tosimultaneously move the shell bodies in opposite directions along thestraight line. This provides quicker operation as both shell bodies maymove at the same time. The shell bodies may adapt more easily to theheight of the pipeline section.

Preferably, the assembly comprises a lock for locking the shell bodiesclosed. This may provide additional security when the shell bodies arepressurized during injection molding. Preferably, the lock is manuallyoperable. This may provide a simple lock mechanism. Preferably, the lockis power assisted. This may provide additional locking force.

Preferably, the assembly is coupled to an injection molding machine.This may provide a more compact working environment around the injectionmolding machine. The assembly may be transported with the injectionmolding machine.

Preferably, the motorized opening and closing of the shell bodies ispowered by an injection molding machine. This may harness power readilyavailable from an injection molding machine.

According to an eighth aspect of the present invention, there isprovided an assembly for supporting a bent pipeline section, wherein theassembly comprises a base and a pair of arms extending from the base,wherein each arm comprises a respective clamping collar for clamping abent pipe section between the arms, wherein each of the clamping collarshas a cylindrical clamping face with a central axis and wherein thecentral axes of the clamping faces are non-parallel. The clampingcollars may hold the bent pipeline section purely at or near, its endsbecause orientation of the clamping collars relative to each otherresists rotation of the a bent pipeline under the effect of gravity.This enables coating material to be applied uninterrupted between theends of the pipeline section. This provides an improved coating.

Preferably, the central axes of the clamping faces are substantiallyco-planar. A central plane of a bent pipeline section may be positionedin line with the axes of the cylindrical clamping faces. This may enablethe clamping collars to clamp a bent pipeline section with less packingmaterial and/or adjustment at the interface therebetween.

Preferably, the plane of the central axes of the clamping faces issubstantially parallel to the base. A central plane of a bent pipelinesection may be positioned in line with the base so that when the base ison a factory floor, a bent pipeline section may be orientated in anatural position for approaching a bent pipeline section mold.

Preferably, the arms are adjustably coupled to the base for supportingdifferent sizes of bent pipeline sections. This facilitates versatilityand re-use of the assembly.

Preferably, the base is equipped with support wheels or support rollers.This facilitates mobility of the assembly and bent pipe sections clampedthereto. Preferably, the support wheels are configured to run on rails.This facilitates controlled movement of the assembly so that it mayapproach a bent pipeline section mold in a pre-defined direction.Likewise, the assembly may be moved to a specific parking area forcooling of a recently-applied coating.

Preferably, the clamping collars are operable by threaded fasteners.Threaded fasteners, like, for example, bolts, nuts or screws facilitateuncomplicated opening and closing of the clamping collars with readilyavailable tools.

In a ninth aspect of the present invention, there is provided a vehiclefor induction heating a bent pipeline section, wherein the vehiclecomprises: a helical induction coil; and wheels arranged to guidemovement of both ends of the induction coil through a tubular insideface of a bent pipeline section. A helical induction coil is naturallyflexible. Movement of the induction coil is determined by the pathfollowed by the wheels as they trundle along the tubular inside face ofthe bent pipeline section. Contact between the wheels and the internalprofile of the bent pipeline section steers the induction coil throughthe bent pipeline section. This may help to prevent contact between theinduction coil and bent pipeline section which may damage the inductioncoil, and any coating the coil may have, and helps to prevent a shortcircuit between the coil and the bent pipeline section.

Preferably, the vehicle comprises a first wheel chassis supportingwheels proximal a first end of the induction coil and a second wheelchassis supporting wheels proximal a second end of the induction coilopposite to the first end thereof. This provides a more balanced supportto the induction coil.

Preferably, the first wheel chassis and the second wheel chassis arecoupled to each other by an elongate bar having a longitudinal axis.Overextension of the induction coil may cause the induction coil to sagand possibly contact the bent pipeline section. The bar may help toavoid overextension of the induction coil.

Preferably, the bar is passes through the induction coil. This providesa more compact design of vehicle.

Preferably, the first wheel chassis and the second wheel chassis areeach coupled to the bar by a respective bearing and wherein the bearingspermit pivoting movement of the first wheel chassis and second wheelchassis in relation to the bar in directions normal to the longitudinalaxis of the bar. The locations of the bearings provide a soundarticulation point for the first and second wheel chassis.

Preferably, the bearings are self-aligning to a position where the firstwheel chassis, the second wheel chassis and the bar are aligned. Thisbiases the vehicle into adopting a generally cylindrical profile whichmay facilitate insertion of the vehicle into pipeline sections.

Preferably, each of the first wheel chassis and the second wheel chassiscomprises a plurality of guide wheel assembles each having two wheelswith axes arranged in a line tangential to a curved central axis of abent pipeline section. Thus, the first and second wheel chassis arethemselves guided by the internal profile of the bent pipeline section.

Preferably, each of the first wheel chassis and the second wheel chassiscomprises three guide wheel assembles. The first and second wheelchassis may be supported through 360 degrees about a longitudinal axisthough the induction coil.

Preferably, the guide wheel assembles of each of the first wheel chassisand the second wheel chassis are arranged at equiangular intervals abouta longitudinal axis though the induction coil.

Preferably, the induction coil is connectable to an external inductionheating power supply. This may avoid the need for an on-board inductionheating power supply.

Preferably, the vehicle comprises at least one socket for electricalconnection of the induction coil to an external induction heating powersupply. This may avoid the need to thread a permanent electricalconnection through an end of a bent pipe section before use of thevehicle. Instead, the vehicle may be pushed though a bent pipelinesection and connected to an induction heating power supply cable at theend.

Preferably, the at least one socket comprises a socket arranged proximaleach end of the vehicle and wherein the sockets provide mechanicalconnection for pulling the vehicle from each end of the vehicle. Thismay allow induction heating power supply cables to perform two roles.

Preferably, the induction coil is equipped with electrically insulativespacers protruding from the outer profile of the induction coil.Preferably, or alternatively, the induction coil clad is in aninsulative sheath. These measures may provide additional protectionagainst contact between the induction coil and bent pipeline section.

In a tenth aspect of the present invention, there is provided a methodof coating a pipeline section with molten coating material with a moldof the first aspect supported by the assembly of the seventh aspect,wherein the method comprises the steps of: a) locating a pipelinesection in the mold and sealing the mold about the pipeline section; b)connecting the mold to a molten coating material delivery pipe from aninjection molding machine; c) injecting molten coating material from aninjection molding machine into the mold until a cavity between the moldand the pipeline section is substantially full of coating material; d)disconnecting the molten coating material delivery pipe from the mold;and e) removing the coated pipeline section from the mold.

Preferably, the pipeline section is a bent pipeline section and themethod comprises an additional step of supporting the bent pipelinesection with the eighth aspect of the present invention before locatingthe bent pipeline section in the mold.

Preferably, the method comprises an additional step of supporting thecoated bent pipeline section with said assembly at a location remotefrom said mold after the step of removing the coated bent pipelinesection from the mold. This may allow the bent pipeline section and itscoating material to cool while the injection molding machine is used forother purposes.

Preferably, the pipeline section is a bent pipeline section and themethod comprises an additional step of induction heating the bentpipeline section with the vehicle of the ninth aspect of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail withreference to the following drawings of which:

FIG. 1 shows a perspective view of an IMPP injection molding machine forfactory-applied coating of steel pipeline sections with a mold andpipeline section on a pipeline section stand;

FIG. 2 shows a plan view of the IMPP injection molding machine of FIG.1;

FIG. 3 shows a side elevation view of a mold support frame assembly witha mold;

FIG. 4 shows a front elevation view the mold support frame assembly witha mold;

FIG. 5 shows a perspective view of parts of the mold support frameassembly with a mold;

FIG. 6A shows a perspective view of a bent pipeline section coated inpolypropylene and supported by a pipeline section stand assembly;

FIG. 6B shows a plan view of the bent pipeline section coated inpolypropylene supported by the pipeline section stand assembly shown inFIG. 6B

FIG. 7A shows a perspective view of a master template used for makingthe mold in FIG. 4;

FIG. 7B shows a perspective plan view of the master template of FIG. 7A;

FIG. 8 shows a perspective view of the mater template of FIG. 7A cladwith layers of glass-fiber matting, high temperature epoxy resin andaccelerators;

FIG. 9 shows a perspective view of the glass-fiber matting of FIG. 8covered in additional high temperature epoxy resin;

FIG. 10 shows a perspective view of an upper shell of the mold in FIG.4;

FIG. 11 shows a vertical cross-sectional view of a thick major profilesection;

FIG. 12 shows a vertical cross-sectional view of a thin major profilesection;

FIG. 13 shows a vertical cross-sectional view of an H-shaped majorprofile section;

FIG. 14 shows a plan view of detail Z in FIG. 13;

FIG. 15 shows a vertical cross-sectional view of a thick median profilesection;

FIG. 16 shows a vertical cross-sectional view of a thin minor profilessection;

FIG. 17 shows a horizontal cross-sectional view X-X of the mold in FIG.4;

FIG. 18 shows a perspective view of the an upper shell and a lower shellof a mold similar to the mold in FIG. 4 in an open position;

FIG. 19 shows a perspective view of an internal pipeline heating coilassembly;

FIG. 20 shows a cross-sectional view of the internal pipeline heatingcoil assembly of FIG. 19; and

FIG. 21 shows a horizontal cross-sectional view of the bent pipelinesection exposing the internal pipeline heating coil assembly inside.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 5, an IMPP injection molding machine 10 forfactory-applied coating of steel pipeline sections comprises a mainsupport frame 20 onto which are mounted an extruder assembly 40, anaccumulator assembly 60, a mold support frame assembly 80, and ahydraulic control circuit 110. Typically, these components are connectedtogether by nuts and bolts so that the IMPP machine 10 may bedisassembled and packed into a container for transportation from factoryto factory. When reassembled for use in a factory, the control circuit110 is connected to a hydraulic power supply from a generator or a shoresupply. The main support frame 20, the extruder assembly 40, theaccumulator assembly 60, the mold support frame assembly 80, and thecontrol circuit 100 each have lifting pints (not shown) to facilitatedisassembly and reassembly of the IMPP injection molding machine 10 withthe help of an overhead crane.

The main frame assembly 20 comprises a generally rectangular main frame22 made of steel and support wheels 24 in the middle and at each end ofthe main frame 22 so that it can be rolled back and forth in thedirection of the double-headed arrow A.

The extruder assembly 40 comprises an extruder hopper 42 and an extruder44 having an inlet 46 in communication with the hopper 42 and an outlet48. The hopper 42 is configured to receive polypropylene pellets fedautomatically from a material conditioning machine. In use, the extruder44 heats the polypropylene pellets from a solid state to a molten stateand pumps the molten polypropylene from the extruder outlet 48, via anextruder delivery pipe 50 and a non-return valve 52, to the accumulatorassembly 60. The output capacity of the extruder 42 is approximately 290kg per hour.

The accumulator assembly 60 comprises a pair of accumulators 62 a, 62 baligned in parallel with each other. Each accumulator 62 a, 62 bcomprises a cylindrical reservoir 64 a,64 b having a port 66 a,66 b incommon communication with an outlet 52 a from the non-return valve 52.Each accumulator 62 a, 62 b further comprises a hydraulically poweredaccumulator ram 68 a, 68 b coupled to an end its respective reservoir 64a,64 opposite to its respective port 66 a,66 b. The ports 66 a, 66 b arein common communication with an accumulator delivery pipe 70 which isconfigured for connection to an IMPP mold. In use, the reservoirs 64 a,64 b have a maximum capacity of 100 liters of molten polypropylene fromthe extruder 44 i.e. a total of 200 liters of molten polypropylene.However, the reservoirs 64 a, 64 b are filled to the volume of moltenpolypropylene required to do a coating on a pipeline section, plus somecontingency molten polypropylene. Next, the accumulator rams 68 a, 68 bforce the molten polypropylene from the reservoirs 64 a,64 b, though theports 66 a,66 b and into the accumulator delivery pipe 70. The moltenpolypropylene is blocked by the non-return valve 52 from returning intothe extruder assembly 40.

The mold support frame assembly 80 comprises a mold support frame 82having a generally C-shape when view from one side, as is best shown inFIG. 3. The mold support frame 82 has an upper support arm 84 and alower support arm 86, both of which are arranged generally horizontal innormal use. An upper support plate 88 is fastened to the underside ofthe upper support arm 84 and a lower support plate 90 is fastened to thetop of the lower support arm 86 facing the upper support plate 88. Theupper 88 and lower 90 support plates have a generally arc shape whenviewed from above, as is best shown in FIG. 2. A pair of guide rails 92a, 92 b, both of which are arranged generally vertical in normal use,are connected between the upper 88 and lower 90 support plates. One ofthe guide rails 92 a, 92 b is on each side of the upper 88 and lower 90support plates, as is best shown in FIG. 4. The mold support frameassembly 80 further comprises an upper mold plate 94 located directlybelow the upper support plate 88, a lower mold plate 96 located directlyabove the lower support plate 90 and an array of hydraulic support framerams 98. The upper 94 and lower 96 mold plates have a generally arcshape, when viewed from above, with the same arc radius as the shape ofthe upper 88 and lower 90 support plates. The guide rails 92 a, 92 bguide sliding movement of the upper 94 and lower 96 mold plates in bothdirections along the guide rails. The support frame rams 98 areconfigured to force the upper 94 and lower 96 mold plates together (upto a force of about 400 kN), in the direction of arrows B, and retractthe upper 94 and lower 96 mold plates apart, in the direction of arrowsC. The mold support frame assembly 80 further comprises a manuallyoperable locking arrangement 100 for pulling and hooking the upper 94and lower 96 mold plates together. The locking arrangement 100 providesadditional force to the support frame rams 98.

The upper 88 and lower 90 support plates and the upper 94 and lower 96mold plates have a generally arc shape to suit a pipeline section mold200 like that shown in FIGS. 1, 3 and 4. The upper 94 and lower 96 moldplates are perforated with a multitude of fixture holes 102 forfasteners to connect IMPP molds having a range of different arc sweepangles (i.e. 90, 82.9, 45 and 15 degrees) and radii. If an irregularmold has shape that is beyond the range acceptable for fastening to theupper 94 and lower 96 mold plates then these may be replaced by a pairof different mold plates to suit the irregular mold. An example of suchan irregular mold would be for coating a T-joint pipeline section or anS-shaped pipeline section.

The pipeline mold 200 comprises an upper shell 202 a and a lower shell202 b mating with the upper shell 202 a along a central plane CP. Theupper shell 202 a and the lower shell 202 b are, with the exception ofminor details, a mirror image of each other about the central plane CP.The upper shell 202 a is fastened below the upper mold plate 94 and thelower shell 202 b is fastened to the top of the lower mold plate 96. Inuse, the support frame rams 98 are used to force the upper 202 a andlower 202 b shells together, in the direction of arrows B, or retractthe upper 202 a and lower 202 b shells, in the direction of arrows C.The upper 202 a and lower 202 b shells open and close in a generallyvertical direction rather than open and close in a pivoting clamshell-style.

The upper 88 and lower 90 support plates, the upper 94 and lower 96 moldplates, the support frame rams 98 and the upper 202 a and lower 202 bshells (i.e. those components shown in FIG. 5) may be disassembled andreplaced so that the IMPP injection molding machine 10 may be used for awide variety of shapes and sizes of pipeline molds for coating, forexample, straight, bent and irregular pipeline sections.

The hydraulic control circuit 110 is housed in a hydraulic valve stand112 which is mounted upon main support frame 20. An operator working theIMPP injection molding machine 10 may control the control circuit 110remotely via wired, or wireless, connection. The control circuit 110provides user-operable control of, amongst other things, theaccumulators 62 a, 62 b and the support frame rams 98.

Referring to FIGS. 6A and 6B, a bent pipeline section 120 coated in apolypropylene coating 122 is supported at each end 124 a,124 b of thebent pipeline section 120 by a pipeline section stand 140 comprising astand base 142 and a pair of stand arms 144 a,144 b extending up fromthe stand base 142. The bent pipeline section 120 shown is carbon steelfor use in oil and gas pipelines with a wall thickness of 12.7 mm and anoutside diameter of 209 mm. The thickness of the polypropylene coating122 may be in the range of, but not limited to, 25 mm to 75 mm. The bentpipeline section 120 is bent in an arc having a sweep angle α of 82.9degrees and an arc radius AR of approximately five times greater thanthe outside diameter of the bent pipeline section.

The stand base 142 has flanged wheels 146 arranged to run along rails Rin a factory floor so that the pipeline section stand 140 may bemaneuvered in a controlled and accurate manner in relation to the moldsupport assembly 80 in both the directions of double-headed arrow A. Thetop of each stand arm 144 a, 144 b has a clamping collar 148 a,148 bwhich is clamped around an end 124 a,124 b of the bent pipeline section120. Each clamping collar 148 a, 148 b comprises a hemi-cylindrical face150 a,150 b formed in the top of a respective stand arm 144 a,144 b.Each clamping collar 148 a, 148 b further comprises a hemi-cylindricalbracket 152 a,152 b detachably fastened by bolts 154 to its respectivestand arm 144 a,144 b and facing its respective hemi-cylindrical face150 a,150 b. PTFE (Polytetrafluoroethylene) tape, strips or thin bar maybe used to help the clamping collars 148 a, 148 b grip the ends 124a,124 b of the bent pipeline section 120.

The bent pipeline section 120 has a curved central axis CA which followsa curved path through the tubular centre of the bent pipeline section120. When the bent pipeline section 120 is inside the bent pipeline mold200 the central axis CA is in the central plane CP between the upper 202a and lower 202 b shells.

The central axis of the first clamping collar 148 a is tangential to thecentral axis CA of the bent pipeline section 120 at the first end 124 athereof and the central axis of the second clamping collar 148 b istangential to the central axis CA of the bent pipeline section 120 atthe second end 124 b thereof opposite to the first end 124 a. Thecentral axes of the first 148 a and second 148 b clamping collars arenon-parallel and co-planar with the central plane CP of the pipelinesection mold 200. Thus, the first 148 a and second 148 b clampingcollars hold the bent pipeline section 120 with its central axis CA inthe central plane CP of the mold 200 without need for support betweenthe ends 144 a,144 b of the bent pipeline section 120.

The bottom of each stand arm 144 a, 144 b has a foot 156 a,156 b whichis fastened to the stand base 142. The stand base 142 is perforated witha multitude of fixture holes 158 for fasteners to connect the stand arms144 a,144 b to bent pipeline sections having a range of different arcsweep angles α (i.e. angle α=90, 82.9, 45 or 15 degrees) and radii AR.

The bent pipeline section 120 shown in FIGS. 6A and 6B has already beencoated in the polypropylene coating 122 by the mold 200 injected withmolten polypropylene by the IMPP injection molding machine 10. The bentpipeline stand assembly 140 holds the bent pipeline section 120 at aheight H from the stand base 142 while the bent pipeline section 120 isbeing moved into the mold 200 before the injection molding process. Thepipeline section stand assembly 140 holds the bent pipeline section 120firmly and accurately in the central plane CP in the mold 200 during theinjection molding process. Also, the pipeline section stand assembly 140holds the bent pipeline section 120 after the injection molding processwhen it has been released from the mold 200 to cool and properlysolidify.

The upper 202 a and lower 202 b shells of the pipeline section mold 200are substantially a mirror image of each other about the central planeCP which divides the upper 202 a and lower 202 b shells. Theconstruction of the upper shell 202 a shall be described, it beingunderstood that this description applies equally to the lower shell 202b in all but very minor details.

A distinct advantage of the construction of the pipeline section mold200 is its versatility for use with different shapes and sizes ofpolypropylene coating and pipeline sections.

Referring to FIGS. 7A to 10 and 17, the upper shell 202 a comprises animpervious shell body 220 made of glass-fiber reinforced plastic(hereinafter referred to as GFRP) clad with an exoskeleton 240 made ofsteel for its reinforcement, stability and non-distensible properties.The shell body 220 is fabricated from glass-fiber matting layered over amaster template 300 and bonded together by a high temperature epoxyresin and accelerator. The exoskeleton 240 is fabricated from laser-cutsteel parts which are assembled, interlocked and welded together. Epoxyresins capable of withstanding temperatures up to, and in excess of 200°centigrade are commercially available and are not discussed in any moredetail.

The shape of the inside face 204 of the upper shell 202 a is defined bya master template 300. The pipeline section mold 200 and the mastertemplate 300 each have a curved central axis which follows the samecurved path as the curved central axis CA of the bent pipeline section120. For simplicity, the central axis of the pipeline section mold 200and the master template 300 shall hereon be referred to as the centralaxis CA.

The master template 300 is constructed from a multitude ofinter-connectable parts of varying shapes and sizes according to theshape and size of the inside face of the shell body 220. In the exampleshown, the master template 300 is constructed from a base template 302supporting an array of wooden semi-circular discs 304, 306, 308, 310,314 interconnected by a wooden curved wall 316 made of plywood oranother suitably workable type of wood. The array of semi-circular discs304, 306, 308, 310, 314 is laid with the discs' flat faces on a flatrecessed part 318 of the base template 302. The central axes ofsemi-circular discs 304, 306, 308, 310, 314 are arranged tangential tothe curved central axis CA and the discs' flat faces are coplanar withthe central plane CP of the pipeline section mold 200. The curved wall316 follows the path of the curved central axis CA.

The wooden semi-circular discs 304, 306, 308, 310, 314 are positionedalong the array according to the thickness of polypropylene coating 122to be applied to the bent pipeline section 120 at certain places alongthe central axis CA. Likewise, the height of the curved wall 316 (fromthe recessed part 318 of the base template 302) varies according to thethickness of polypropylene coating 122 to be applied to the bentpipeline section 120 at certain places along the central axis CA. Theoutline 320 of the flat recessed part 318 of the base template 302corresponds to the outer rims 222 l, 222 s of the shell body 220. Thebase template 302 is made from wood and the recessed part 318 is cutfrom the wood with a router or other machining tool.

Major diameter semi-circular discs 304 are arranged along the middleapproximately 80 percent of the central axis CA at intervals ofapproximately 100 mm to 200 mm. The major diameter semi-circular discs304 correspond to a main section 206 of the pipeline section mold 200where the polypropylene coating 122 is thickest.

Minor diameter semi-circular discs 306 are arranged along the finalapproximately two percent of the central axis CA at the end of thepipeline section mold 200. Since this is a small length of pipelinemold, one minor diameter semi-circular disc 306 at each end of this partof the central axis CA is sufficient. The minor diameter semi-circulardiscs 306 correspond to a sealed section 208 of the pipeline sectionmold 200 which has the outside diameter of the ends 124 a, 124 b of thebent pipeline section 120 and which is sealed from polypropylenecoating.

Median diameter semi-circular discs 308 are arranged along approximatelyeight percent of the central axis CA of the pipeline section mold 200inside where the minor diameter semi-circular discs 306 are arranged.Since this is a small length of pipeline mold, a median diametersemi-circular disc 308 at each end of this part of the central axis CAis sufficient. The median diameter semi-circular discs 308 correspond toa restricted section 210 of the pipeline section mold 200 where thepolypropylene coating 122 is thinnest.

A chamfered semi-circular disc 310 is arranged at a transition between amajor semi-circular disc 304 and a median semi-circular disc 308 neareach end of the central axis CA. Each chamfered semi-circular disc 310tapers from the diameter of the adjacent major semi-circular disc 304 tothe diameter of the adjacent median semi-circular disc 308 with a smoothconical face 312. The chamfered semi-circular disc 310 provides aconical section 212 of the pipeline section mold 200 where moltenpolypropylene destined for the restricted section 210 may pass smoothly.This helps to prevent, or at least minimise, voids in the restrictedsection's polypropylene coating 122.

An infill semi-circular disc 314 is arranged at the midpoint of thelonger side 2061 of the main section 206 of the pipeline section mold200. The infill semi-circular disc 314 corresponds to an infill section214 of the pipeline section mold 200 at the point where the accumulatordelivery pipe 70 is connected and molten polypropylene is injected intothe pipeline section mold 200 from the IMPP injector machine 10.

The semi-circular discs 304, 306, 308, 310, 314 and the curved wall 316of the master template 300 may be re-used to make multiple pipelinesection molds 200 having the same basic shape. The number and shape ofthe semi-circular discs 304, 306, 308, 310, 314, the curved wall 316 andthe shape of the base template 302 may be changed to make a new mastertemplate for making different molds capable of producing polypropylenecoatings having different outer shapes and thickness to suit differentpipeline sections used for different purposes. Alternatively, thesemi-circular discs 304, 306, 308, 310, 314 may be substituted by asolid master template made of plastics material or GFRP.

The shell body 220 is fabricated with multiple sheets of glass-fibermatting, high temperature epoxy resin and accelerator layered over themaster template 300. First, the array of semi-circular discs 304, 306,308, 310, 314 and the curved wall 316 are located in the recessed part318 of the base template 302. Next, the interstices between the array ofsemi-circular discs 304, 306, 308, 310, 314 and the curved wall 316 arefilled with high density foam and then shaped with a smooth finishprimer. This is to prevent the shell body 220 from sagging intointerstices between the semi-circular discs 304, 306, 308, 310, 314.

Referring to FIG. 8, glass-fiber matting 221 and high temperature epoxyresin with accelerator 223 are laid in an initial base layer 224 ofapproximately 8 mm thick over the array of semi-circular discs 304, 306,308, 310, 314 and the curved wall 316. The recessed parts 318 of thebase template 302 not occupied by the array of circular discs 304, 406,308, 310, 314 receive glass-fiber matting 221 and high temperature epoxyresin with accelerator 223 approximately 8 mm thick. This forms a rim222 l, 222 s of approximately 30 mm to 50 mm wide along each of thelonger 202 a 1 and shorter 202 as sides of the upper shell 202 a,respectively, which is also part of the initial base layer 224.

Referring to FIG. 9, the base layer 224 of glass-fiber matting 221 andhigh temperature epoxy resin with accelerator 223 is covered inadditional epoxy resin with accelerator 223. The exoskeleton 240 ispartially embedded into the base layer 224 of glass-fiber matting whilethe epoxy resin is still soft so that the exoskeleton 240 adheres firmlyto base layer 224 once the epoxy resin is set.

Referring to FIG. 10, the exoskeleton 240 is constructed from an array342 of steel profiled sections 244, 246, 248, 250, 252 arranged atvarious stages along the length of the pipeline section mold 200. Theprofiled sections 244, 246, 248, 250, 252 have inner hemi-cylindricalfaces the axes of which are arranged tangential to the curved centralaxis CA of the pipeline section mold 200. The profiled sections 244,246, 248, 250, 252 are connected to a steel curved spine 258 thatextends along the length of the exoskeleton 240 in line with the centralaxis CA of the pipeline section mold 200. Also, these profiled sections244, 246, 248, 250, 252 are connected to a steel curved inner rim 260and a steel curved outer rim 262 which extend along the length of theexoskeleton 240 on the shorter side 202 as and the longer side 202 a 1of the upper shell 202 a, respectively. The profiled sections 244, 246,248, 250, 252 have lower flat faces which are parallel to the centralplane CP of the pipeline section mold 200.

Referring in particular to FIG. 11, a thick major profiled section 244comprises an arch 2442 with an inner hemi-cylindrical face 2444 centeredon the central axis CA, a lower flat face 2446, 2448 at each end of thearch 2442 arranged parallel to the central plane CP, and a head piece2450 at the apex of the arch 2442. One lower flat face 2446 has a rebate2447 which accommodates the curved inner rim 260 and the other lowerflat face 2448 has a rebate 2449 which accommodates the curved outer rim262. The inner hemi-cylindrical face 2444, at the head piece 2450, has arebate 2451 which accommodates the curved spine 258. The curved innerrim 260, the curved outer rim 262 and the curved spine 258 are welded tothe thick major profiled section 244 at the lower flat face 2446, thelower flat face 2448 and the head piece 2450, respectively. The headpiece 2450 comprises a blind threaded bore 2454 for receiving a threadedfastener F. The blind threaded bore 2454 acts as a pick-up point forconnecting the upper shell 202 a to the upper mold plate 94 with saidfastener F. The difference in the radius of the inner hemi-cylindricalface 2444 and the radius of the next major semi-circular disc 302(either within the inner hemi-cylindrical face 2444 or adjacent thereto)is the same as the approximately 8 mm thickness BLT of the base layer224 of glass-fiber matting and epoxy resin. The thick major profiledsection 244 is laser cut, for precision, from steel 20 mm thick toprovide extra strength to the thick major profiled section 244 withenough thickness to accommodate the blind threaded bore 2454. The innerhemi-cylindrical face 2444 is partially embedded into the base layer 224of glass-fiber matting while the epoxy resin is still soft to help keythe thick major profiled section 244 into the base layer 224 once theepoxy resin has cured.

Referring in particular to FIG. 12, a thin major profiled section 246comprises an arch 2462 with an inner hemi-cylindrical face 2464 centeredon the central axis CA and a lower flat face 2466, 2468 at each end ofthe arch 2462 arranged parallel to the central plane CP. One lower flatface 2466 has a rebate 2467 which accommodates the curved inner rim 260and the other lower flat face 2468 has a rebate 2469 which accommodatesthe curved outer rim 262. The apex of the inner hemi-cylindrical face2464 has a rebate 2471 which accommodates the curved spine 258. Thecurved inner rim 260, the curved outer rim 262 and the curved spine 258are welded to the thin major profiled section 246 at the lower flat face2466, lower flat face 2468 and the apex of the apex of the arch 2462,respectively. The difference in the radius of the inner hemi-cylindricalface 2464 and the radius of the next major semi-circular disc 304(either within the inner hemi-cylindrical face 2464 or adjacent thereto)is the same as the approximately 8 mm thickness BLT of the base layer224 of glass-fiber matting and epoxy resin. The thin major profiledsection 246 is laser cut, for precision, from steel 10 mm thick. Theinner hemi-cylindrical face 2444 is partially embedded into the baselayer 224 of glass-fiber matting while the epoxy resin is still soft.

Referring in particular to FIGS. 13 and 14, an H-shaped major profiledsection 248 comprises an arch 2482 with a flat top face 2483 and aninner hemi-cylindrical face 2484 centered on the central axis CA, a sidewall 2486, 2488 welded to each side face 2485 of the arch 2482 andarranged perpendicular to the arch 2482 thereby giving the H-shapedmajor profiled section 248 an H-shape when viewed from above the uppershell 202 a. A rebate 2487 below one side wall 2486 and the arch 2482accommodates the curved inner rim 260. A rebate 2489 below the otherside wall 2488 and the arch 2482 accommodates a hemi-cylindricalprofiled section 2491 around the infill semi-circular disc 314 withabout 8 mm spare to form the infill section 214 of the initial baselayer 224 located therebetween. The apex of the inner hemi-cylindricalface 2484 has a rebate 2493 which accommodates the curved spine 258. Thecurved inner rim 260 is welded to bottom of a region between the arch2482 and one side wall 2486. The curved spine 258 is welded to the arch2482. A break in the curved outer rim 262 is bridged by the other sidewall 2488 which is welded to both parts of the curved outer rim 262, asis best shown by FIG. 14. The arch 2482 and both side walls 2486, 2488comprise blind threaded bores 2494 for receiving a respective threadedfastener F. The blind threaded bores 2494 acts as pick-up points forconnecting the upper shell 202 a to the upper mold plate 94 with saidfasteners F. The difference in the radius of the inner hemi-cylindricalface 2484 and the radius of the next adjacent major semi-circular disc302 is the same as the approximately 8 mm thickness BLT of the baselayer 224 of glass-fiber matting and epoxy resin. The components of thethick major profiled section 244 are laser cut, for precision, fromsteel 20 mm thick. The inner hemi-cylindrical face 2484 is partiallyembedded into the base layer 224 of glass-fiber matting while the epoxyresin is still soft to help key the H-shaped major profiled section 248into the base layer 224 once the epoxy resin has cured.

Referring in particular to FIG. 15, a thick median profiled section 250comprises an arch 2502 with an inner hemi-cylindrical face 2504 centeredon the central axis CA, a lower flat face 2506,2508 at each end of thearch 2502 arranged parallel to the central plane CP, and a head piece2510 at the apex of the arch 2502. One lower flat face 2506 has a rebate2507 which accommodates the curved inner rim 260 and the other lowerflat face 2508 has a rebate 2509 which accommodates the curved outer rim262. The head piece 2510 part of the hemi-cylindrical face 2504 has arebate 2511 which accommodates the curved spine 258. The curved innerrim 260, the curved outer rim 262 and the curved spine 258 are welded tothe thick median profiled section 250 at the lower flat face 2506, lowerflat face 2508 and head piece 2510, respectively. The head piece 2510comprises a pair of blind threaded bores 2514 for receiving a respectivethreaded fastener F. The blind threaded bores 2514 act as a pick-uppoints for connecting the upper shell 202 a to the upper mold plate 94with said fastener F. The difference in the radius of the innerhemi-cylindrical face 2504 and the radius of the median semi-circulardisc 308 (either within the inner hemi-cylindrical face 2504 or adjacentthereto) is the same as the approximately 8 mm thickness BLT of the baselayer 224 of glass-fiber matting and epoxy resin. The thick medianprofiled section 250 is laser cut, for precision, from steel 20 mmthick. The inner hemi-cylindrical face 2504 is partially embedded intothe base layer 224 of glass-fiber matting while the epoxy resin is stillsoft to help key the thick median profiled section 250 into the baselayer 224 once the epoxy resin has cured.

Referring in particular to FIG. 16, a thin minor profiled section 252comprises an arch 2522 with an inner hemi-cylindrical face 2524 centeredon the central axis CA and a lower flat face 2526,2528 at each end ofthe arch 2522 arranged parallel to the central plane CP. One lower flatface 2526 has a rebate 2527 which accommodates the curved inner rim 260and the other lower flat face 2528 has a rebate 2529 which accommodatesthe curved outer rim 262. The apex of the inner hemi-cylindrical face2524 has a rebate 2531 which accommodates the curved spine 258. Thecurved inner rim 260, the curved outer rim 262 and the curved spine 258are welded to the thin minor profiled section 252 at the lower flat face2526, lower flat face 2528 and the arch 2522, respectively. Thedifference in the radius of the inner hemi-cylindrical face 2524 and theradius of the minor semi-circular disc 306 is the same as theapproximately 8 mm thickness BLT of the base layer 224 of glass-fibermatting and epoxy resin. The thin minor profiled section 252 is lasercut, for precision, from steel 10 mm thick. The inner hemi-cylindricalface 2524 is partially embedded into the base layer 224 of glass-fibermatting while the epoxy resin is still soft. The thin minor profiledsection 252 is relatively thin to help avoid air pockets while at thesame time helping to key the thin minor profiled section 252 into thebase layer 224 once the epoxy resin is set.

Referring in particular to FIGS. 10 and 17, the parts of the exoskeleton240 are interlocked and welded together with a thin minor profiledsection 252 at each extreme end of the central axis CA where the sealedsection 208 of the upper shell 202 a is located. Going inwards along thecentral axis CA from the thin minor profiled section 252, a thick medianprofiled section 250 is next to each thin minor profiled section 252where the restricted section 210 meets the conical section 212 of theupper shell 202 a. Next, a thin major profiled section 246 is next toeach thick median profiled section 250 where the conical section 212meets the main section 206 of the upper shell 202 a. The thin majorprofiled section 246 is clad with a shoulder 246 a on each side of thecentral axis CA to provide additional support when connected to theupper mold plate 94. Next, a thick major profiled section 244 and thenanother thin major profiled section 246 are arranged between the thinmajor profiled sections 246 and the H-shaped major profiled section 248.The thick major profiled section 244 is clad with a shoulder 244 a oneach side of the central axis CA to provide additional support whenconnected to the upper mold plate 94. At the midpoint along the centralaxis is the H-shaped major profiled section 248. The profiled sections244, 246, 248, 250, 252, the curved spine 258, the curved inner rim 260and the curved outer rim 262 respectively, are embedded into the baselayer 224 while the epoxy resin remains soft. Vents 260 v, 262 v throughthe curved inner rim 260 and the curved outer rim 262 permit passage ofepoxy resin to help key the exoskeleton into the base layer 224.

Fabrication of the shell body 220 continues. A reinforcement layer 226of glass-fiber matting 221 and high temperature epoxy resin withaccelerator 223 are layered up to approximately 20 mm thick over thebase layer 224 and the exoskeleton 240 (with the exception of the topfaces of the profiled sections). Many of those parts of the exoskeletonthat are spared the reinforcement layer 226 are used as connectionpoints to the upper 94 and the lower 96 mold plates of the mold supportassembly. The reinforcement layer 226 of matting of glass-fiber matting221 and high temperature epoxy resin with accelerator 223 provides theshell body with additional strength. The overall thickness of the base224 and reinforcement 226 layers of glass-fiber matting 221 and hightemperature epoxy resin with accelerator 223 is up to approximately 28mm.

When the resin has completely has cured, the upper 202 a and lower 202 bshells can withstand molten polypropylene of up to 200 degreescentigrade. The exoskeleton 240 embedded into glass-fiber matting 221and epoxy resin 223 of the base 224 and reinforcement 226 layers addsconsiderable strength and accuracy to the upper 202 a and lower 202 bshells. This results in a pipeline section mold 200 which is capable ofwithstanding a pressure generated by the IMPP injection molding machine10 of up to 200 bar (20,000,000 Pa). Also, the construction of the upper202 a and lower 202 b shells provides a lighter and cheaper pipelinesection mold 200 than can be made from solid steel. The construction ofthe upper 202 a and lower 202 b shells is quicker than casting andmachining a special shape of pipeline section mold from steel. Once asteel mold has been machined it can be used for only one shape ofpipeline coating. Whereas the construction method using a mastertemplate 300 to make a GFRP shell body 220 reinforced with exoskeleton240 is versatile and can be used for various different shapes ofpipeline section mold whilst conserving many of the components used inmaking previous pipeline section molds.

Referring to FIGS. 7A and 7B, the master template 300 is used toconstruct both the upper shell 202 a and the lower shell 202 b of thepipeline section mold 200 because, as mentioned above, they are a mirrorimage of each other in all but very minor details. The followingdescribes construction of the upper shell 202 a, but it applies equallyto the lower shell 202 b. The master template 300 produces a relativelysmooth inside face 204 on the upper shell 202 a of the pipeline sectionmold 200. The major 304, median 308 and chamfered 310 semi-circulardiscs define the main 306, restricted 210 and conical 212 sections ofthe upper shell 202 a, respectively. The main 306, restricted 210 andconical 212 sections surround the bent pipeline section 120 into whichmolten polypropylene coating 122 is injected by the IMPP machine 10. Theminor semi-circular discs 306 define the restricted sections 210 of theupper shell 202 a which seal the ends 124 a, 124 b of the pipelinesection 120 to prevent escape of the molten polypropylene. Thesemi-circular infill disc 214 defines the shape of the point of theupper shell 202 a that is coupled to the accumulator delivery pipe 70.The recessed part 318 of the base template 302 defines the extent of thelonger rim 222 l and the shorter rim 220 s of the shell body 220.

Referring to FIG. 18, the upper shell 202 a is fastened to the uppermold plate 94, by fasteners F through the fixture holes 102, at thepick-up points of the thick major profiled section 244, the H-shapedmajor profiled section 248 and the thick median profiled section 250 ofthe upper shell's exoskeleton 240. Likewise, the lower shell 202 b isfastened to the lower mold plate 96, by fasteners F through the fixtureholes 102, at the pick-up points of the thick major profiled section244, the H-shaped major profiled section 248 and the thick medianprofiled section 250 of the lower shell's exoskeleton 240. As mentionedabove, the guide rails 92 a, 92 b of the mold support assembly 80 guidesliding movement of the upper 94 and lower 96 mold plates so that theupper 202 a and the lower 202 b shells can be opened and closed along avertical axis V-V of the guide rails 92 a,92 b. This is a neater,smaller and less complex solution than a clam-style opening as is usedwith all-steel IMPP molds for bent pipeline sections.

Referring to FIGS. 19 to 21, an internal pipe heating assembly 400 is avehicle which comprises a copper induction coil 402 arranged in a tighthelix spanning a first wheel chassis 410 a at one end of the internalpipe heating assembly 400 and a second wheel chassis 410 b at anopposite end of the internal pipeline heating assembly 400. The firstwheel chassis 410 a and second 410 b wheel chassis are connected by anelongate tie-bar 440 defining a longitudinal axis. The internal pipelineheating assembly 400 is manually pulled back and forth inside the bentpipeline section 120 by a first cable 430 a connected to the first wheelchassis 410 a and a second cable 430 b connected to the second wheelchassis 410 b. The tie bar 430 restricts expansion and contraction ofthe distance between the first 410 a and second 410 b wheel chassisalong the longitudinal axis of the tie-bar 430. Alternatively, theinternal pipeline heating assembly 400 may be manually pulled back andforth inside the bent pipeline section 120 by cords (not shown)connected to an eyelet on the first wheel chassis 410 a and acorresponding eyelet 428 on the second wheel chassis 410 b.

The first 430 a and second 430 b cables are substantially the same,albeit pointing in opposite directions in relation to the longitudinalaxis of the tie bar 440. The construction of the first cable 430 a shallbe described, it being understood that this description applies equallyto the second cable 430 b. The first cable 430 a comprises at its corean electrical power supply cable 432 surrounded by an insulating sheath434. The first cable 430 comprises a plug 436 for electrical andmechanical connection to a socket 412 in the first wheel chassis 410 a.The plug 426 is detachably connected to the socket 412 by any mechanicalconnection capable of withstanding tension in the cables 430 a,430 bused to pull the internal pipeline heating assembly 400 through a bentpipeline section 120, like, for example, a twist-operated bayonetfitting or a threaded fitting.

The first 410 a and second 410 b wheel chassis of the internal pipelineheating assembly 400 are substantially the same, albeit pointing inopposite directions in relation to the longitudinal axis of the tie bar440. The construction of the first wheel chassis 410 a shall bedescribed, it being understood that this description applies equally tothe second wheel chassis 410 b.

The first wheel chassis 410 a comprises the socket 412 mounted to thecentre of a circular end cap 414 made of rigid insulative material. Thesocket 412 protrudes through the circular end cap 414 from the side ofthe plug 436 to the opposite side of the circular end cap 414 where itsupports a gland 416 protruding from the centre of the socket 412. Thegland 416 comprises a conductive material and it supports an electricalconnection 418. The socket 412 and the plug 436 are made of insulativematerial. The electrical supply cable 432 is electrically coupled to afirst end of the induction coil 402 via the gland 416 and the electricalconnection 418 when the plug 436 is received in the socket 412.

The first wheel chassis 410 a comprises three guide wheel assemblies 420each having a pair of freely-rotatable guide wheels 422 on the same sideof the circular end cap 414 as the socket 412 and an elongate bar 424 onthe opposite side of the circular end cap 414. The guide wheelassemblies 420 are arranged at equiangular intervals of 120 degreesabout the longitudinal axis of the tie bar 440.

Each of the three pairs of guide wheels 422 is arranged to run along theinside of the bent pipeline section 120, as is best shown in FIG. 21.One guide wheel 422 of each pair leads the other guide wheel 422 of thepair in whichever direction of movement that the first wheel chassis 410a takes through the tubular inside face of the bent pipeline section120. The axes of each pair of wheels 422 are arranged in a linetangential to the curved central axis CA of the bent pipeline section120. Thus, the first wheel chassis 410 a is guided along the curvedcentral axis CA by contact between the internal profile of the bentpipeline section 120 and the pairs of guide wheels 422. The first wheelchassis 410 a follows the path of the central axis CA faithfully. Thefirst wheel chassis 410 a is supported by the pairs of guide wheels 422through 360 degrees about the central axis CA.

The three elongate bars 424 protrude away from the circular end cap 414inside about 20 percent of the length of the induction coil 402 wherethey connect to a circular support block 426 made of rigid insulativematerial. The circular support block 426 has smaller diameter than theinside diameter of the induction coil 402 so that it fits inside. Thecircular support block 426 has larger diameter than a circlecircumscribed by the three elongate bars 424 about the longitudinal axisof the tie bar 430. The circular end cap 414 has a diameterapproximately the same as the outside diameter of the induction coil 402both of which are approximately ten percent smaller than the insidediameter of the bent pipeline section 120 so that internal pipelineheating assembly 400 fits inside.

The tie-bar 440 comprises a self-aligning bearing 442 a,442 b at, ornear, each end of the tie bar 440. One bearing 442 a is housed at thecentre of the first wheel chassis's circular support black 426. Theother bearing 442 b is housed at the centre of the second wheelchassis's circular support black 426. Copper is inherently ductile andthe induction coil 402 behaves like a spring. The self-aligning bearings442 a,442 b and the induction coil 402 permit pivoting movement of theend caps 414, and therefore the whole of the first 410 a and second 410b wheel chassis, in relation to the tie bar 430 in both of the x axisand the y axis. The x and y axes are orthogonal and they occupy a planeperpendicular to the longitudinal axis of the tie bar 440. However, theself-aligning bearings 442 a,442 b and resilience in the helicalinduction coil 402 tend to return, or maintain, the induction coil 402and the elongate bars 424 in line with the longitudinal axis of the tiebar 430 so that the internal pipeline heating assembly 400 naturallyadopts a generally cylindrical shape.

The helical induction coil 402 is coated with an insulative rubbersilicon sleeve 404 to prevent a short circuit between the bent pipelinesection 120 and the indication coil 402. Gaps at regular interval along,and around, the helical induction coil 402 are occupied by button-shapedspacers 406 made of insulative material like, for example, PTFE. Thespacers 406 help to maintain a space between the inside of the bentpipeline section 120 and the indication coil 402. This helps to reduceany wear on the rubber silicon sleeve 404 that may be caused by frictionwith the inside of the bent pipeline section 120.

In use, the induction coil 402 of the internal pipeline heating assembly400 is supplied with an electrical supply from a user-operable inductionheating generator (not shown). The electrical supply to the inductioncoil 402 is variable by an operator within a range of 20 to 180 Volts,30 to 700 Amperes and 400 to 500 Hz to achieve the right heatdistribution and temperature in the bent pipeline section 120.

In use, the internal pipeline heating assembly 400 is manually pulledback and forth inside the bent pipeline section 120 by the first 430 aand second 430 b cables at something, like, for example, one meter perminute. The induction coil 402 induces eddy currents in the adjacentpart of the steel bent pipeline section 120 to cause localized heatingof the bent pipeline section 120. The first wheel chassis 410 a guidesmovement of one half of the induction coil 402 and the second wheelchassis 410 b guides movement of the other half of the induction coil402 through the tubular inside face of the bent pipeline section 120.Articulation in the self-aligning bearings 442 a, 442 b and elasticityin the induction coil 402 allows the internal pipeline heating assembly400 to adapt to the inner profile of the bent pipeline section 120. Theinduction coil 402 follows the path of the central axis CA faithfully.

The process of coating a new uncoated steel bent pipeline section 120 isdescribed as follows. Initially, a first thin layer of a primer, such asan epoxy-based material, is applied in either liquid or powdered form tothe outer surface of the steel bent pipeline section 120. To ensure agood bond between the bent pipeline section 120 and the primer, the bentpipeline section 120 is typically blast cleaned and etched with anappropriate anchor pattern.

A second layer of polypropylene that has been chemically modified to actas an adhesive is applied over the primer during the curing time of theprimer. While curing of the primer is ongoing a third layer ofpolypropylene is applied.

The IMPP injection molding machine 10 is started by an operator. Theextruder 44 heats polypropylene pellets from a solid state to a moltenstate in preparation for pumping the molten polypropylene to theaccumulators 62 a, 62 b.

The stand arms 144 a, 144 b are fastened to the stand base 142 in anorientation suited to receive the shape of the bent pipeline section120. The ends 124 a, 124 b of the bent pipeline section 120 are clampedto the clamping collars 148 a,148 b of at top of the stand arms 144a,144 b with the central axis CA in a generally horizontal plane.

An operator connects the internal pipeline heating assembly 400 to anelectrical supply from an induction heating generator and pulls theinternal pipeline heating assembly 400 back and forth, at about onemeter per minute, along the inside of the bent pipeline section 120using the cables 430 a, 430 b. This may be done automatically if anappropriate winch system is available. The electrical current in theinduction coil 402 induces eddy currents in the steel bent pipelinesection 120 to cause localized heating of up to about 180 degreescentigrade. The operator uses an infrared heat sensor to detect heatdistribution and moves the internal pipeline heating assembly 400 toachieve as near to even heat distribution in the bent pipeline section120 as is possible. If necessary, the operator may vary the speed atwhich the internal pipeline heating assembly 400 is pulled back andforth in the bent pipeline section 120. Articulation in theself-aligning bearings 442 a, 442 b and elasticity in the induction coil402 allows the internal pipeline heating assembly 400 to adapt to thecurve of the bent pipeline section 120 and navigate its way throughwithout becoming stuck. The internal pipeline heating assembly 400preheats the bent pipeline section 120 before the process of coatingwith the third layer of polypropylene begins. The third layer ofpolypropylene coating 122 is applied over the first layer of primer andthe second layer of chemically modified polypropylene during the curingtime of the primer so as to allow the layers to bond. Pre-heating thesteel of the bent pipeline section 120 helps avoid short fill of thepipeline section mold 200 and improves adherence of the polypropylenecoating 122 to the primer and the bent pipeline section 120.

The bent pipeline section 120 and the bent pipeline section standassembly 140 are rolled towards the IMPP injection molding machine 10with upper 202 a and lower 202 b shells of the pipeline section mold 200held on an open position by the mold support assembly 80. The bentpipeline section 120 is maneuvered to the centre of the upper 202 a andlower 202 b shells. The orientation of the stand arms 144 a, 144 b issuch that the pipeline section mold 200 fits in the middle with littlespace to spare so that an operator can see when the bent pipelinesection 120 is correctly positioned in relation to the pipeline sectionmold 200.

The control circuit 110, under the control of an operator who may be ata remote location, causes the support frame rams 98 to close the upper202 a and lower 202 b shells of the pipeline section mold 200 tightly byapplying a pressure of up to 200 bar (20,000,000 Pa). The sealedsections 208 of the upper 202 a and lower 202 b shells grip and seal theends 124 a,124 b of the bent pipeline section 120. Any slightmisalignment between the bent pipeline section 120 and the pipelinesection mold 200 is corrected by engagement between the bent pipelinesection 120 and the sealed sections 208 of the upper 202 a and lower 202b shells. The bent pipeline section stand assembly 140 can roll a smalldistance on the rails R to allow this correction. The infill section 214of the upper 202 a and lower 202 b shells forms a connection point forthe accumulator delivery pipe 70. The connection point is reinforced bythe H-shaped major profile section 248.

The extruder 44, under the control of the operator, pumps moltenpolypropylene from the extruder outlet 48, through the extruder deliverypipe 50, past the non-return vale 52 and into the accumulators 62 a, 62b via their ports 66 a, 66 b until the accumulator reservoirs 64 a,64 bare sufficiently full.

The accumulator delivery pipe 70 is connected to the infill section 214of the pipeline section mold 200. The operator causes the accumulatorrams 68 a,68 b to steadily force molten polypropylene at a pressure ofup to 200 bar (20,000,000 Pa) from the accumulator reservoirs 64 a,64 b,back through the ports 66 a, 66 b (but not the non-return valve 52 whichprevents re-entry of molten polypropylene into the extruder assembly40), through the accumulator delivery pipe 70, and injects it into thecavity between the main 206 section, the conical sections 212, and therestricted sections 210 of the pipeline section mold 200 and the bentpipeline section 120.

The internal pipeline heating assembly 400 continues to heat the bentpipeline section 120 while the process of polypropylene coating the bentpipeline section 120 with is ongoing. This is to help avoid short fillof the pipeline section mold 200 and improve adherence of thepolypropylene coating 122 to the primer and the bent pipeline section120.

When the IMPP injection molding machine 10 detects that the moltenpolypropylene has filled the cavity between the pipeline section mold200 and the bent pipeline section 120 injection from the IMPP injectionmolding machine 10 automatically ceases. Filling of the pipeline sectionmold 200 typically takes about 15 minutes, although the time taken willvary according to the size of the bent pipe line section 120 and thepipeline section mold 200. The operator removes the internal pipelineheating assembly 400 from within the bent pipeline section 120 anddisconnects it from its induction heating generator supply. Cooling andsolidifying of the polypropylene coating 122 begins.

Eventually, the polypropylene coating 122 is sufficiently cool and solidto be released from the pipeline section mold 200. An operatordisconnects the accumulator delivery pipe 70 from the infill section 214of the pipeline section mold 200 and severs any residual polypropylenein the accumulator pipe 70 from an injection point 126 of thepolypropylene coating 122. The control circuit 110, under the control ofthe operator, causes the support frame rams 98 to open the upper 202 aand lower 202 b shells of the pipeline section mold 200 wide enough torelease the bent pipeline section 120. The bent pipeline section standassembly 140 can be rolled away from the mold support assembly 80 on therails R to a location remote from the IMPP injection molding machine 10.The bent pipeline section stand assembly 140 acts as a cooling frame forthe recently coated bent pipeline section 120 which can cool slowly.Meanwhile, the IMPP injection molding machine 10 is ready for injectionmolding a new polypropylene coating 122 around another bent pipelinesection 120.

1. An assembly for supporting a mold comprising a plurality of mutuallyseparable shell bodies for coating a pipeline section with moltencoating material from an injection molding machine, wherein the assemblycomprises motorized opening and closing of the shell bodies in astraight line.
 2. The assembly of claim 1, wherein the assemblycomprises adjustable support for supporting molds of different sizes. 3.The assembly of claim 1, wherein the assembly comprises adjustablesupport for supporting molds for coating irregular pipeline sections orbent pipeline sections.
 4. The assembly of claim 1, wherein themotorized opening and closing is guided by rails.
 5. The assembly ofclaim 1, wherein the motorized opening and closing is operable tosimultaneously move the shell bodies in opposite directions along thestraight line.
 6. The assembly of claim 1, wherein the assembly iscoupled to an injection molding machine.
 7. An assembly for supporting abent pipeline section, wherein the assembly comprises a base and a pairof arms extending from the base, wherein each arm comprises a respectiveclamping collar for clamping a bent pipe section between the arms,wherein each of the clamping collars has a cylindrical clamping facewith a central axis and wherein the central axes of the clamping facesare non-parallel.
 8. The assembly of claim 7, wherein the central axesof the clamping faces are substantially co-planar.
 9. The assembly ofclaim 8, wherein the plane of the central axes of the clamping faces issubstantially parallel to the base.
 10. The assembly of claim 7, whereinthe arms are adjustably coupled to the base for supporting differentsizes of bent pipeline sections.
 11. A vehicle for induction heating abent pipeline section, wherein the vehicle comprises: a helicalinduction coil; and wheels arranged to guide movement of both ends ofthe induction coil through a tubular inside face of a bent pipelinesection.
 12. The vehicle of claim 11, wherein the vehicle comprises afirst wheel chassis supporting wheels proximal a first end of theinduction coil and a second wheel chassis supporting wheels proximal asecond end of the induction coil opposite to the first end thereof. 13.The vehicle of claim 12, wherein the first wheel chassis and the secondwheel chassis are coupled to each other by an elongate bar having alongitudinal axis.
 14. The vehicle of claim 13, wherein the bar passesthough the induction coil.
 15. The vehicle of claim 13, wherein thefirst wheel chassis and the second wheel chassis are each coupled to thebar by a respective bearing and wherein the bearings permit pivotingmovement of the first wheel chassis and second wheel chassis in relationto the bar in directions normal to the longitudinal axis of the bar. 16.The vehicle of claim 15, wherein the bearings are self-aligning to aposition where the first wheel chassis, the second wheel chassis and thebar are aligned.
 17. The vehicle of claim 12, wherein each of the firstwheel chassis and the second wheel chassis comprises a plurality ofguide wheel assembles each having two or three wheels with axes arrangedin a line tangential to a curved central axis of a bent pipelinesection.
 18. The vehicle of claim 11, wherein the vehicle comprises atleast one socket for electrical connection of the induction coil to anexternal induction heating power supply or the vehicle comprises atleast one socket comprising a socket arranged proximal each end of thevehicle and wherein the sockets provide mechanical connection forpulling the vehicle from each end of the vehicle.
 19. The vehicle ofclaim 11, wherein the induction coil is equipped with electricallyinsulative spacers protruding from the outer profile of the inductioncoil.